The present invention relates to expandable styrene polymer compositions, to processes for producing expandable styrene polymers, and to products having high mechanical robustness. The invention further relates to processes for producing styrene polymer foam materials, to the expandable styrene polymers and also the styrene polymer foam materials themselves, and to the various uses of the expandable styrene polymers and of the foam materials.
Various foam materials have been used for decades as materials of construction for a variety of applications. Starting products suitable for producing foam materials include styrene, butadiene, and other unsaturated compounds. With the monomers it is possible to obtain polymers which then, often with use of a blowing agent, can be converted, with expansion, into foam materials.
In the course of the operation of producing them, expandable styrene polymers, i.e., more particularly, polymers having a fraction of at least 50 percent of styrene units in the polymer, are often admixed with further components, e.g., auxiliary components, such as white oil. This has proven advantageous for styrene homopolymers as well.
In this context, further components are added frequently in an amount of 0.05%-5% for purposes which include that of enhancing the foam-forming behavior of the polymers. White oils (in other words paraffins) also act as flow improvers and plasticizers. These components also lower the glass transition temperature of the polymer matrix. The use of white oils in the production of expandable polymers also has drawbacks.
The term “white oil” may be understood to encompass a liquid mixture of aliphatic, linear or branched hydrocarbons or functionalized hydrocarbons (generally having an average molar mass of around 300-3000 g/mol). The molar mass distribution of different white oil batches and grades may also be subject to great fluctuations.
The selection of the further component has consequences for the properties of the foam material and for the processing quality of the expandable composition. Where, for example, the white oil has a relatively high low-molecular-mass fraction, the glass transition point of the polymer in which it is used will be lowered. As a consequence, the resultant expandable styrene polymer composition may exhibit highly divergent expansion characteristics.
The styrene polymer foam materials obtained then also have different mechanical strengths. A further drawback of the known use of white oil is that, when other additives are added with white oil, the expandable styrene polymer composition exhibits a marked deterioration in mechanical strength, such as compressive strength and flexural strength, as compared with a styrene polymer foam without white oil.
Various methods are described in the prior art for how further components (auxiliaries for polymers) may be obtained. Thus, for example, WO 1999/32427 describes a process for hydrogenating benzene polycarboxylic acids, in which various cyclohexanecarboxylic esters are obtained. These reaction products can be used as plasticizers in plastics. DE-A 10 032 580 describes plasticizers, for various plastics, that can be obtained starting from phthalic esters.